Does it rain more on weekends, or is Long Island's recent weather pattern just bad luck?

Are weekends rainier than the workweek?

If the question sounds preposterous, consider this spring: Including the sodden Memorial Day weekend we just experienced, it rained five of the last six weekends.

It rained on half, or 10, of 20 weekend days since the start of the season on March 20. By comparison, it rained on a mere one-third of the 46 workweek days.

Was this uneven distribution a function of chance? A cosmic conspiracy to ruin your golf game? Is there a scientific explanation?

"Really, this is not much more than a bit of a bad luck pattern," said Newsday meteorologist Geoff Bansen. "Look at the global jet stream," the bands of strong wind that generally blow from west to east all across the globe, affecting temperature and precipitation, he said. "The movement is very rhythmic, but no one bats an eye when these things happen during the week."

Finding a pattern to weekend rainfall, he added, would likely require sifting decades of climate data, not just a season’s worth.

A Newsday analysis of decades of precipitation data collected by the National Weather Service in Islip suggested Bansen was correct: Analyses of five, 10 and 40 years of data found rain was not more frequent on weekends than weekdays. It also found no statistically significant change in the overall occurrence of rain events. The analysis did find that, over the last five years, Thursday was the rainiest day, followed by Saturday.

A number of academic studies have analyzed historical precipitation data from other regions in search of weekly weather cycles, or what is sometimes called a "weekend effect." One hypothesis is that human activity that releases aerosols — tiny particles from smoke, dust or other sources that float in the atmosphere — could have meteorological impacts including on precipitation occurrence and amounts. Since that activity tends to increase during the week and decrease during the weekend, the thinking goes, it might be possible to discern cyclical variance.

But the results of these studies are mixed. A 2008 paper found that "both the average area and intensity" of rain events over the southeast United States were greater in the middle of the week than on weekends; the phenomenon was reversed over the Atlantic.

A 2007 paper, analyzing 40 years of data from 219 surface observing stations in the United States, found "no statistically significant weekly cycles," noting that while the body of literature continued to grow, new results "sometimes confirm and sometimes contradict previous studies."

A 2012 review of roughly 40 studies of the topic concluded that it was difficult to determine if large-scale weekly cycles existed at all, or, that if they did exist, they might be indistinguishable from natural climate variability. In an email, Arturo Sanchez-Lorenzo, the paper’s lead author, wrote that "if real the signal is very low and without significant effect" on people’s daily experience. The "subjective component" is probably stronger, he continued: "a rainy day on Sunday is more inconvenient for the people as it is a day off."

Jase Bernhardt, an assistant professor of geology, environment and sustainability at Hofstra University, said he would want to see 30 years of climate data, preferably from multiple locations, before signing on to the notion of a weekend effect here on the Island or anywhere else.

"You try to slice up these data sets in all these different ways, and inevitably, you will find random patterns that at first seem like something meaningful." But often, he said, "when you peel back the data, look at an appropriate sample size, you realize it goes away, there wasn’t anything actually meaningful here."